yaml is a YAML parser and serialiser for JavaScript. Parsing a YAML document with a version of yaml on the 1.x branch prior to 1.10.3 or on the 2.x branch prior to 2.8.3 may throw a RangeError due to a stack overflow. The node resolution/composition phase uses recursive function calls without a depth bound. An attacker who can supply YAML for parsing can trigger a RangeError: Maximum call stack size exceeded with a small payload (~2–10 KB). The RangeError is not a YAMLParseError, so applications that only catch YAML-specific errors will encounter an unexpected exception type. Depending on the host applications exception handling, this can fail requests or terminate the Node.js process. Flow sequences allow deep nesting with minimal bytes (2 bytes per level: one [ and one ]). On the default Node.js stack, approximately 1,000–5,000 levels of nesting (2–10 KB input) exhaust the call stack. The exact threshold is environment-dependent (Node.js version, stack size, call stack depth at invocation). Note: the librarys Parser (CST phase) uses a stack-based iterative approach and is not affected. Only the compose/resolve phase uses actual call-stack recursion. All three public parsing APIs are affected: YAML.parse(), YAML.parseDocument(), and YAML.parseAllDocuments(). Versions 1.10.3 and 2.8.3 contain a patch.
Weakness
The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Yaml | Eemeli | 1.0.0 (including) | 1.10.3 (excluding) |
| Yaml | Eemeli | 2.0.0 (including) | 2.8.3 (excluding) |
| Node-yaml | Ubuntu | upstream | * |